HP 3PAR VMware ESX Implementation Guide

Figure 19 LUN Set to Round Robin
Managing a round robin I/O path policy scheme through the VI/vSphere client GUI for a large
network can be cumbersome and challenging to maintain because the policy must be specified
for each LUN individually and then updated when new devices are added. Alternatively, VMware
provides a way for the server administrator to use esxcli, vCLI, or vSphere Management Assistant
(vMA) commands to manage I/O path policy for storage devices on a per-host basis using
parameters defined in a set of native ESX/ESXi storage plug-ins.
The VMware native multipathing has two important plug-ins:
• The Storage Array Type Plug-in (SATP) — handles path failover and monitors path health.
• The Path-selection Plug-in (PSP) — chooses the best path and routes I/O requests for a specific
logical device, that is, PSP defines the path policy.
The correct ESX/ESXi host Storage Array Type Plug-in (SATP) to be used is related to the HP 3PAR
array host persona:
• When HP 3PAR host persona 6/Generic-legacy is the host persona in use with an ESX/ESXi
host, use the SATP VMW_SATP_DEFAULT_AA.
• When HP 3PAR host persona 11/VMware is the host persona in use with an ESX/ESXi host,
use the SATP VMW_SATP_ALUA.
For ESX/ESXi 4.0 versions (4.0 GA through all 4.0 updates), the default SATP rules must be edited
in order to automatically achieve a round robin I/O path policy for storage devices.
Beginning with ESX/ESXi 4.1, additional custom SATP rules can be created that target SATP/PSP
to specific vendors while leaving the default SATP rules unmodified. The custom SATP can be used
to automatically achieve a round robin I/O path policy for storage devices.
Configuring ESX/ESXi Multipathing for Round Robin via SATP PSP
As part of the PSP Round-Robin configuration, the value of IOPS can be specified. IOPS is the
number of IO operations scheduled for each path during path changes within the Round-Robin
path selection scheme. The default IOPS value is 1000. HP recommendsIOPS=1 as an initial value
42 Configuring the Host for a Fibre Channel Connection